Proteomic identification and functional validation of activins and bone morphogenetic protein 11 as candidate novel muscle mass regulators.
Myostatin is a secreted TGF-beta family member that controls skeletal muscle growth. Humans, cattle, and dogs carrying natural loss-of-function mutations in the myostatin gene and myostatin knockout mice exhibit significant increases in skeletal muscle mass. Treatment of adult mice with antimyostatin antibodies also resulted in significant muscle mass increases. However, myostatin-knockout mice that were treated with a soluble form of the activin type II receptor (ActRII) B increased their muscle mass by an additional 15-25%, indicating that there is at least one additional ligand, in addition to myostatin, that functions to limit muscle growth. Here, both soluble ActRII and -IIB fragment-crystallizable proteins were used to affinity purify their native ligands from human and mouse sera. Using mass spectrometry-based proteomics and in vitro binding assays we have identified and confirmed that a number of TGF-beta family members, including myostatin, activins-A, -B, and -AB, bone morphogenetic proteins (BMPs) -9, -10, and -11, bind to both ActRIIs. Many of these factors, such as BMPs-11, -9, and -10 were discovered in systemic circulation for the first time, indicating that these ligands may also act in an endocrine fashion. Using a promoter-specific gene reporter assay, we demonstrated that soluble ActRIIB fragment-crystallizable proteins can inhibit the canonical signaling induced by these ligands. In addition, like myostatin, these factors were able to block the differentiation of myoblast cells into myotubes. However, in addition to myostatin, only BMP-11, and activins-A, -B, and -AB could be blocked from inhibiting the myoblast-to-myotube differentiation with both soluble ActRIIs, thus implicating them as potential novel regulators of muscle growth.
Souza
Tatyana A
TA
Department of Biological Technologies, Wyeth Research, Cambridge, Massachusetts 02149, USA.
Chen
Xuan
X
Guo
Yongjing
Y
Sava
Parid
P
Zhang
Jimin
J
Hill
Jennifer J
JJ
Yaworsky
Paul J
PJ
Qiu
Yongchang
Y
D030301:Activin Receptors, Type II / Q000276:immunology; D028341:Activins / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D055412:Growth Differentiation Factors / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D024510:Muscle Development / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D011485:Protein Binding; D040901:Proteomics; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000378:metabolism
D019485:Bone Morphogenetic Proteins; C119153:Gdf11 protein, mouse; D055412:Growth Differentiation Factors; D007141:Immunoglobulin Fc Fragments; D016212:Transforming Growth Factor beta; D028341:Activins; D030301:Activin Receptors, Type II; C425584:activin receptor type II-B